Detecting an invalid date Date instance in JavaScript

Question

I d like to tell the difference between valid and invalid date objects in JS  but couldn t figure out how   var d   new Date  foo    console log d toString        shows  Invalid Date  console log typeof d      shows  object  console log d instanceof Date      shows  true    Any ideas for writing an isValidDate function    Ash recommended Date parse for parsing date strings  which gives an authoritative way to check if the date string is valid  What I would prefer  if possible  is have my API accept a Date instance and to be able to check assert whether it s valid or not  Borgar s solution does that  but I need to test it across browsers  I also wonder whether there s a more elegant way  Ash made me consider not having my API accept Date instances at all  this would be easiest to validate  Borgar suggested testing for a Date instance  and then testing for the Date s time value  If the date is invalid  the time value is NaN  I checked with ECMA-262 and this behavior is in the standard  which is exactly what I m looking for

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Instead of using new Date   you should use   var timestamp   Date parse  foo     if  isNaN timestamp     false      var d   new Date timestamp       Date parse   returns a timestamp  an integer representing the number of milliseconds since 01 Jan 1970   It will return NaN if it cannot parse the supplied date string

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If you use io-ts  you can use the decoder DateFromISOString directly   import   DateFromISOString   from  io-ts-types lib DateFromISOString   const decoded   DateFromISOString decode  2020-05-13T09 10 50 957Z

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Too many complicated answers here already  but a simple line is sufficient  ES5     Date prototype isValid   function  d    return  isNaN Date parse d         or even in ES6    Date prototype isValid   d   gt   isNaN Date parse d

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Maybe I m late but I have a solution  const isInvalidDate    dateString    gt  JSON stringify new Date dateString        null    const invalidDate   new Date  Hello    console log isInvalidDate invalidDate      true  const validDate   new Date  2021 02 08    console log isInvalidDate validDate      false

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Would like to mention that the jQuery UI DatePicker widget has a very good date validator utility method that checks for format and validity  e g   no 01 33 2013 dates allowed    Even if you don t want to use the datepicker widget on your page as a UI element  you can always add its  js library to your page and then call the validator method  passing the value you want to validate into it   To make life even easier  it takes a string as input  not a JavaScript Date object   See  http   api jqueryui com datepicker   It s not listed as a method  but it is there-- as a utility function   Search the page for  parsedate  and you ll find     datepicker parseDate  format  value  settings   - Extract a date from a string value with a specified format   Example usage   var stringval    01 03 2012   var testdate   try     testdate     datepicker parseDate  mm dd yy   stringval                   Notice  yy  indicates a 4-digit year value   catch  e     alert stringval     is not valid   Format must be MM DD YYYY             and the date value must be valid for the calendar         More info re specifying date formats is found at http   api jqueryui com datepicker  utility-parseDate   In the above example  you wouldn t see the alert message since  01 03 2012  is a calendar-valid date in the specified format   However if you made  stringval  equal to  13 04 2013   for example  you would get the alert message  since the value  13 04 2013  is not calendar-valid   If a passed-in string value is successfully parsed  the value of  testdate  would be a Javascript Date object representing the passed-in string value   If not  it d be undefined

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For int 1-based components of a date   var is valid date   function year  month  day        var d   new Date year  month - 1  day       return d getFullYear       year  amp  amp   d getMonth     1      month  amp  amp  d getDate       day      Tests       is valid date 2013  02  28   amp  amp   is valid date 2016  02  29   amp  amp   is valid date 2013  02  29   amp  amp   is valid date 0000  00  00   amp  amp   is valid date 2013  14  01

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This just worked for me  new Date  foo       Invalid Date     is true   However this didn t work  new Date  foo        Invalid Date     is false

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IsValidDate  function date            var regex     d 1 2    d 1 2    d 4            if   regex test date   return false          var day   Number date split      1            date   new Date date           if  date  amp  amp  date getDate      day  return false          return true

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So I liked  Ask Clarke answer with little improvement by adding try catch block for dates which cannot go through var d   new Date d  -  function checkIfDateNotValid d            try              var d   new Date d               return   d getTime       d getTime       NAN is the only type which is not equal to itself           catch  e               return true

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None of these answers worked for me  tested in Safari 6 0  when trying to validate a date such as 2 31 2012  however  they work fine when trying any date greater than 31   So I had to brute force a little  Assuming the date is in the format mm dd yyyy  I am using  broox answer   Date prototype valid   function         return isFinite this          function validStringDate value       var d   new Date value       return d valid    amp  amp  value split      0      d getMonth   1      validStringDate  2 29 2012       true  leap year  validStringDate  2 29 2013       false validStringDate  2 30 2012       false

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I ve written this function  Pass it a string parameter and it will determine whether it s a valid date or not based on this format  dd MM yyyy      here is a test  input   hahaha  output  false   input   29 2 2000  output  true    input   29 2 2001  output  false    function isValidDate str        var parts   str split           if  parts length  lt  3          return false      else           var day   parseInt parts 0            var month   parseInt parts 1            var year   parseInt parts 2            if  isNaN day     isNaN month     isNaN year                 return false                    if  day  lt  1    year  lt  1              return false          if month gt 12  month lt 1              return false          if   month    1    month    3    month    5    month    7    month    8    month    10    month    12   amp  amp  day  gt  31              return false          if   month    4    month    6    month    9    month    11    amp  amp  day  gt  30              return false          if  month    2                if    year   4     0  amp  amp   year   100     0       year   400     0  amp  amp   year   100     0                     if  day  gt  29                      return false                else                   if  day  gt  28                      return false                                        return true

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This function validates a string date in digit formats delimited by a character  e g  dd mm yyyy  mm dd yyyy     Param     1 the date in string data type  2  optional - string - default is      the date delimiter  most likely     or  -  3  optional - int - default is 0  the position of the day component when the date string is broken up via the String split function  into arrays  4  optional - int - default is 1  the position of the month component when the date string is broken up via the String split function  into arrays  5  optional - int - default is 2  the position of the year component when the date string is broken up via the String split function  into arrays   Return   a javascript date is returned if the params are OK else null    function IsValidDate strDate  strDelimiter  iDayPosInArray  iMonthPosInArray  iYearPosInArray        var strDateArr    a string array to hold constituents day  month  and year components     var dtDate    our internal converted date     var iDay  iMonth  iYear          sanity check        no integer checks are performed on day  month  and year tokens as parsing them below will result in NaN if they re invalid     if  null    strDate    typeof strDate     string           return null         defaults     strDelimiter   strDelimiter             iDayPosInArray   undefined    iDayPosInArray   0   iDayPosInArray      iMonthPosInArray   undefined    iMonthPosInArray   1   iMonthPosInArray      iYearPosInArray   undefined    iYearPosInArray   2   iYearPosInArray       strDateArr   strDate split strDelimiter        iDay   parseInt strDateArr iDayPosInArray  10       iMonth   parseInt strDateArr iMonthPosInArray  10  - 1     Note  months are 0-based     iYear   parseInt strDateArr iYearPosInArray  10        dtDate   new Date          iYear          iMonth     Note  months are 0-based         iDay        return   isNaN dtDate   amp  amp  dtDate getFullYear      iYear  amp  amp  dtDate getMonth      iMonth  amp  amp  dtDate getDate      iDay    dtDate   null     Note  months are 0-based     Example call   var strDate  18-01-1971    if  null    IsValidDate strDate        alert  invalid date

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My solution is for simply checking whether you get a valid date object   Implementation  Date prototype isValid   function             An invalid date object returns NaN for getTime   and NaN is the only        object not strictly equal to itself      return this getTime       this getTime           Usage  var d   new Date  lol     console log d isValid        false  d   new Date  2012 09 11     console log d isValid        true

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This flavor of isValidDate uses a regular expression that handles leap years   function isValidDate value        return      10 12 0  13578        3 01   12  0-9  0  1-9         1 8-9  d 2     2-9  d 3         11 0  469        30  12  0-9  0  1-9         1 8-9  d 2     2-9  d 3         0 2       2 0-8  1 0-9  0  1-9         1 8-9  d 2     2-9  d 3         0 2       29        2468  048 00       0 2       29        3579  26 00       0 2       29        1  89  0  48        0 2       29        2-9  0-9  0  48        0 2       29        1  89  2468  048        0 2       29        2-9  0-9  2468  048        0 2       29        1  89  13579  26        0 2       29        2-9  0-9  13579  26       test value

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Why i Suggest moment js it is very popular library simple to solve all date and time format timezone problems easy to check string date  valid or not var date   moment  quot 2016-10-19 quot    date isValid    we can t solve simple way to validate all the cases Disspointment if i insert in valid number like 89 90 95 in new Date   above few answare   i am getting bad result however it return true  x000D   x000D  const isValidDate   date   gt     console log  input  date  var date new Date date    console log date  return     Object prototype toString call date        object Date    amp  amp   date    return  isNaN date getTime        var test  05 04 2012  console log isValidDate test      var test  95  console log isValidDate test      var test  89  console log isValidDate test      var test  80  console log isValidDate test      var test  badstring  console log isValidDate test   x000D   x000D   x000D

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shortest answer to check valid date  if  isNaN date getTime

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Date prototype toISOString throws RangeError  at least in Chromium and Firefox  on invalid dates  You can use it as a means of validation and may not need isValidDate as such  EAFP   Otherwise it s   function isValidDate d      try         d toISOString        return true        catch ex          return false

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date parse valueToBeTested   gt  0 is all that s needed  A valid date will return the epoch value and an invalid value will return NaN which will fail  gt  0 test by virtue of not even being a number   This is so simple that a helper function won t save code though it might be a bit more readable  If you wanted one   String prototype isDate   function       return  Number isNaN Date parse this        OR  To use    StringToTest  isDate

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Nice solution  Included in my library of auxiliary functions  now it looks like this   Object isDate   function obj         lt summary gt      Determines if the passed object is an instance of Date       lt  summary gt       lt param name  obj  gt The object to test  lt  param gt       return Object prototype toString call obj        object Date       Object isValidDate   function obj         lt summary gt      Determines if the passed object is a Date object  containing an actual date       lt  summary gt       lt param name  obj  gt The object to test  lt  param gt       return Object isDate obj   amp  amp   isNaN obj getTime

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Simple and elegant solution   const date   new Date    year -  month -  day  00 00   const isValidDate    Boolean  date   amp  amp  date getDate      day    sources     1  https   medium com  esganzerla simple-date-validation-with-javascript-caea0f71883c   2  Incorrect date shown in new Date   in JavaScript

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Pure JavaScript solution  const date   new Date year    month-1   day   const isValidDate    Boolean  date   amp  amp  date getDate      day    Also works on leap years  Credit to https   medium com  esganzerla simple-date-validation-with-javascript-caea0f71883c

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function isValidDate strDate        var myDateStr  new Date strDate       if    isNaN   myDateStr getMonth                return true            return false      Call it like this  isValidDate   2015 5 2          gt  true isValidDate   2015 5 2a          gt  false

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you can check the valid format of txDate value with this scirpt  if it was in incorrect format  the Date obejct not instanced and return null to dt     var dt   new Date txtDate value   if  isNaN dt     And as  MiF s suggested  in short way   if isNaN new Date

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For Angular js projects you can use   angular isDate myDate

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None of the above solutions worked for me what did work however is function validDate  d        var date   new Date d       var day    quot  quot    date getDate        if   day length    1   day    quot 0 quot    day      var month    quot  quot     date getMonth     1       if   month length    1   month    quot 0 quot    month      var year    quot  quot    date getFullYear        return    month    quot   quot    day    quot   quot    year      d       the code above will see when JS makes 02 31 2012 into 03 02 2012 that it s not valid

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No one has mentioned it yet  so Symbols would also be a way to go   Symbol for new Date  Peter        Symbol for  Invalid Date      true  Symbol for new Date        Symbol for  Invalid Date      false    x000D   x000D  console log  Symbol for new Date  Peter        Symbol for  Invalid Date     Symbol for new Date  Peter        Symbol for  Invalid Date       true x000D   x000D  console log  Symbol for new Date        Symbol for  Invalid Date     Symbol for new Date        Symbol for  Invalid Date       false x000D   x000D   x000D    Be aware of  https   caniuse com  search Symbol

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Generally I d stick with whatever Date implantation is in the browser stack  Which means you will always get  Invalid Date  when calling toDateString   in Chrome  Firefox  and Safari as of this reply s date    if  Date prototype isValidDate     Date prototype isValidDate   function        return this toDateString   toLowerCase   lastIndexOf  invalid      -1           I did not test this in IE though

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you can convert your date and time to milliseconds getTime    this getTime   Method return Not a Number NaN when not valid   if  isNaN new Date  2012 25 255   getTime       return  valid date time     return  Not a valid date time

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I have seen some answers that came real close to this little snippet  JavaScript way   x000D   x000D  function isValidDate dateObject       return new Date dateObject  toString        Invalid Date     console log isValidDate  WTH        - gt  false console log isValidDate new Date  WTH         - gt  false console log isValidDate new Date         - gt  true x000D   x000D   x000D   ES2015 way   x000D   x000D  const isValidDate   dateObject   gt  new Date dateObject        toString        Invalid Date   console log isValidDate  WTH        - gt  false console log isValidDate new Date  WTH         - gt  false console log isValidDate new Date         - gt  true x000D   x000D   x000D    Updated  To reflect comments

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I combined the best performance results I found around that check if a given object    is a Date instance  benchmark here  has a valid date  benchmark here    The result is the following   function isValidDate input      if   input  amp  amp  input getTimezoneOffset  amp  amp  input setUTCFullYear       return false     var time   input getTime      return time     time

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return String new Date  12 12 2002         quot Invalid Date quot

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A ready function based on top rated answer              Check if date exists and is valid             param  String  dateString Date in YYYY-mm-dd format          function isValidDate dateString      var isValid   false    var date     date       new Date        dateString      if       Object prototype toString call        date        object Date           if  isNaN date getTime                 Date is unreal         else            Date is real if month and day match each other in date and string  otherwise may be shifted         isValid           date getUTCMonth     1     dateString split  -   1    1  amp  amp          date getUTCDate       dateString split  -   2    1            else          It s not a date         return isValid

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The selected answer is excellent  and I m using it as well   However  if you re looking for a way to validate user date input  you should be aware that the Date object is very persistent about making what might appear to be invalid construction arguments into valid ones   The following unit test code illustrates the point   QUnit test   valid date test   function  assert         The following are counter-examples showing how the Date object will      wrangle several  bad  dates into a valid date anyway   assert equal isValidDate new Date 1980  12  15    true     d   new Date      d setFullYear 1980     d setMonth 1     d setDate 33     assert equal isValidDate d   true     assert equal isValidDate new Date 1980  100  150    true       If you go to this exterme  then the checker will fail   assert equal isValidDate new Date  This is junk     false       This is a valid date string   assert equal isValidDate new Date  November 17  1989     true       but is this    assert equal isValidDate new Date  November 35  1989     false         Ha   It s not   So  the secret to working with this version of      isValidDate is to pass in dates as text strings    Hooboy     alert d toString

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I really liked Christoph s approach  but didn t have enough of a reputation to vote it up    For my use  I know I will always have a Date object so I just extended date with a valid   method   Date prototype valid   function       return isFinite this       Now I can just write this and it s much more descriptive than just checking isFinite in code     d   new Date userDate   if  d valid         do stuff

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check whether date is valid var t   new Date  2011-07-07T11 20 00 000 00 00x    valid    isNaN t valueOf

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I think some of this is a long process  We can cut it short as shown below    function isValidDate dateString            debugger          var dateStringSplit          var formatDate           if  dateString length  gt   8  amp  amp  dateString length lt  10                try                   dateStringSplit   dateString split                       var date   new Date                    date setYear parseInt dateStringSplit 2    10                   date setMonth parseInt dateStringSplit 0   10  - 1                   date setDate parseInt dateStringSplit 1   10                     if  date getYear      parseInt dateStringSplit 2  10   amp  amp  date getMonth   1    parseInt dateStringSplit 0  10   amp  amp  date getDate      parseInt dateStringSplit 1  10                         return true                                    else                       return false                                   catch  e                    return false                                  return false

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You can check the validity of a Date object d via  d instanceof Date  amp  amp  isFinite d    To avoid cross-frame issues  one could replace the instanceof check with  Object prototype toString call d        object Date     A call to getTime   as in Borgar s answer is unnecessary as isNaN   and isFinite   both implicitly convert to number

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Yet another way to check whether the date is a valid date object   const isValidDate    date    gt     typeof date      object   amp  amp     typeof date getTime      function   amp  amp      isNaN date getTime

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You can simply use moment js  Here is an example   var m   moment  2015-11-32    YYYY-MM-DD    m isValid       false   The validation section in the documentation is quite clear   And also  the following parsing flags result in an invalid date    overflow  An overflow of a date field  such as a 13th month  a 32nd day of the month  or a 29th of February on non-leap years   a 367th day of the year  etc  overflow contains the index of the invalid unit to match  invalidAt  see below   -1 means no overflow  invalidMonth  An invalid month name  such as moment  Marbruary    MMMM     Contains the invalid month string itself  or else null  empty  An input string that contains nothing parsable  such as moment  this is nonsense     Boolean  Etc      Source  http   momentjs com docs

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Here s how I would do it   if  Object prototype toString call d        object Date           it is a date   if  isNaN d getTime           d valueOf   could also work        date is not valid     else          date is valid       else        not a date     Update  2018-05-31   If you are not concerned with Date objects from other JS contexts  external windows  frames  or iframes   this simpler form may be preferred   function isValidDate d      return d instanceof Date  amp  amp   isNaN d

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Date object to string is more simple and reliable way to detect if both fields are valid date   e g  If you enter this  -------  to the date input field  Some of the above answers won t work   jQuery validator addMethod  greaterThan         function value  element  params            var startDate   new Date   params  val             var endDate   new Date value            if startDate toString        Invalid Date     endDate toString        Invalid Date                 return false            else               return endDate  gt  startDate                   Must be greater than  0

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var isDate    function input            var status   false          if   input    input length  lt   0              status   false            else             var result   new Date input             if  result     Invalid Date                 status   false              else               status   true                                return status

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Inspired by Borgar s approach I have made sure that the code not only validates the date  but actually makes sure the date is a real date  meaning that dates like 31 09 2011 and 29 02 2011 are not allowed   function dateStr        s   dateStr split           d   new Date  s 2   s 1 -1   s 0        if  Object prototype toString call d        object Date              if   isNaN d getTime     amp  amp  d getDate      s 0   amp  amp               d getMonth       s 1  - 1                 return true                      return  Invalid date

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pretty old topic     Try something like this   if     null      JSON stringify new Date  wrong date      console log  correct    else console log  wrong

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Date valid   function str     var d   new Date str     return  Object prototype toString call d        object Date    amp  amp   isNaN d getTime          https   gist github com dustinpoissant b83750d8671f10c414b346b16e290ecf

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I use the following code to validate values for year  month and date   function createDate year  month   date      var d   new Date year  month   date     if  d getFullYear      year         d getMonth      month        d getDate       date        throw  invalid date         return d      For details  refer to Check date in javascript

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function isValidDate date      return     Object prototype toString call date        object Date    amp  amp   date

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